Four course beacon



1 F. J. LUNDBERG I 2,

I FOUR COURSE BEACON Filed June 12, 1943 VO/CE mm. su/w Y Rf? I020 N gnu/ms Sl/PFL Y a INVENTOR.

FRANK J1 LU/VDBERG A TTORNEY Patented Oct. 28, 1947 UNITED STATES PATENT FOUR COURSE BEACON Application June 12, 1943, Serial No. 490,594

Claims.

This invention relates to radio signal systems; and more particularly to systems wherein energy} may be difierently modulated in two independ-' ent channels and supplied from a common source to a desired load in predetermined phase relationship.

It is often desirable to supply energy to a common load, for example, a radio beacon antenna system, this energy being modulated with a first set of signals such as course identifying signals and with other signals such as voice signals. A radio beacon of this character is illustrated in the copending application of A. Alford and N. Marchand, Serial No. 449,258, filed July 1, 1942, now Patent No. 2,414,431, issued January 21, 1947. In such systems it is necessary that a predetermined phase relationship of the carrier frequency supplied to the load and modulated With difierent signals be maintained. Normally, the line feeding energy to the course-identifying arrangement will have radio frequency energy therein with a given percentage modulation. To avoid cross modulation, it has been usual to couple the modulator for other signals to. a part of the source separated from the course-identifying output by one or more stages in the radio frequency source so that the energy furnished the modulator for the other signals may be free of such source modulation. In such systems, however, any tampering with the radio frequency source at a point in advance of the coupling point to the second modulator will cause an upset in the predetermined phase relationship requiring further ad- J'ustment.

It is an object of my invention to provide a coupling arrangement for supplying energy modulated with two different signals from a, common source to a load in such a manner that the phase relationship of the carrier energy supplied to said load will be maintained despite alterations in the characteristic of the radio frequency source circuit.

It is a further object of my invention to provide an arrangement for energizing radio beacons with course-identifying signals and with other signals from a common radio frequency source while maintaining predetermined phase relationship of the carrier bearing each of said modulations at the antenna load.

With these and other objects in view, a better understanding of my invention may be had from a particular description of an embodiment thereof made with reference to the accompanying drawing, the single figure of which shows an application to a four course radio beacon provided With voice signals in addition to the course indi-- cating signals.

In the figure there is shown three antenna elements I, 2 and 3 horizontally disposed in substantially a straight line, elements I and 3 being interconnected by transmission line 4 provided with a transposition 5 and substantially equally spaced from central antenna 2. The other two units 1 and 9 are shown substantially equally spaced on either side of antenna 2 and interconnected by a transmission line 8 provided with a transposition in. As illustrated, the antenna units are horizontal loops of the type more fully described in U. S. Patent No. 2,283,897, issued May "26, 1942. It should be understood, however, that any type of antenna suitable for providing beacons may be used if. desired.

Energy from radio frequency source I5 is applied over variable coupler 23 and line 2! to one terminal of a bridge network 22, the diagonally opposite terminal of which is provided with a balancing network 23. Since one arm of bridge 22 produces a phase reversal of energy, there will be substantially no carrier frequency energy dissipated in network 23. Connected to the other terminals of bridge 22 are lines 26, 2! In which the energy is modulated by mechanical modulators 24 driven by motor 25. Some of the side band energy produced in lines 26 and 2'? will be dissipated in network 23 and some of it will feed back into line 2|. In actual practice it has been found that side band level is such that about 25% modulation of the carrier frequency exists in line 2|.

Lines 26 and 2? feed to conjugate points on bridge network 28. Line 29 is connected to one terminal of bridge 28 to extract therefrom substantially only side band modulated energy which is applied over line 4 and transposition 5 to antenna elements I and 3. From the diagonally opposite terminal of bridge 28 is connected line 30 which applies energy over bridge 40 and line 42 to antenna element 2.

Coupling 20 is preferably a relatively close coupling to furnish substantial power to antennas I, 2 and 3 since there is not amplification beyond this point. Other energy modulated in electronic modulators 52, 53 is supplied to the antenna array comprising antennas I, 9 and 2 to define a course at right angles to that defined by I, 2 and 3. In the application, Serial No. 449,258, referred to above, a similar arrangement is illustrated. However, in the arrangement of that application, energy from the common source is fed from difierent points therein to the separate mod- .in bridge such as (iii.

ation to a terminal of bridge 49.

ulators in order to prevent a carry-over to the electronic modulators of the modulating signals such as existing in line 2|, for example. In such a system, there is generally provided two stages in the radio frequency source between the electronic modulation energy and that supplied directly to the mechanical modulators. This, together with proper choice of line lengths, produces the desired phase relation for balancing out However, if any change is made in either of the two stages of the radio frequency source in advanc of the electronic modulation tapping point, an upset in the phase of energy supplied to the antennaresults, It has been found that such an arrangement is quite critical as to phase adjustments. Accordingly, in order to avoid such an arrangement, I provide a loose coupling it taken directly across line 21 for supplying the radio frequency energy to modulators 52 and 53. This energy is supplied'at line H to input loops l3, [9 of the separate modulators. Only modulator 52 is shown in detail, modulater 53 being shown in block diagram since it is substantially identical in form to 52.

The energy applied at it! is-fed to two grids 54a of the tube of modulator amplifier 52. Thistube is preferably biased so that the energy supplied will drive the tube to saturation. By operating substantially at saturation, the unwanted modulations present on energy supplied from line 2| are substantially eliminated. Voice frequency signals are applied from source i to the input of both modulators 52 and 53. In addition, a course indicating frequency of, for example, 1020 cycles may be supplied to one of the modulators such as 52. These modulating signals are applied to the plates 5 of modulator 52 so as to produce plate modulation of the energy therein. To the corresponding plates of modulator 53'only the voice signals are applied for the reasons set forth later; Modulated radio frequency istaken from the output of modulators 52 and 53 over lines 55 and 56 and applied to diagonally opposite terminals of a bridge network 51.

at one terminal of the bridge but the 1020-cycle energy is not balanced out since it. is applied at only one of the feeding points. Accordingly, this 1020 supply is fed over line 53' and: keying switch E2 to transmission line 8' from which it feeds antennas l and '9. Switch $2 is operated by means of relay El and keyer fill to reverse the polarity of energy supplied to antennas l and-9 periodically to define the desired course line. From the diagonally opposite terminal of bridge 5?, line 59 serves to carry the radio frequency energy, voice modulation, and 1020 cycle vari- Thus, both linesw and 59 carry energy witht-he radio frequency components in phase to bridge Ml'where they are fed together with the modulationsignals over line 42 to antenna 2. A balancing network ll is provided at the diagonally opposite terminal of the bridge 50 to dissipate the side band energy applied from line 35' and 59.

With this circuit arrangement any variation in. the characteristics of source l5'will-not produce any relative phase shift in the energy as applied over lines 33 and 59. Asa consequence,

there will be no off-set in the phase relationship of energy applied to the antenna because: of any adjustment of source therein.

While my invention, as described above-,.has

orufeplacement of tubes been shown applied to a four course beacon, it is clear that the principles thereof apply equally as well to other types of systems. For example, should it be desired to provide only a single beacon such as would be produced by antennas I, 2 and 3 alone, then a single modulator such as 52 might be used and connection made therefrom directly to line 59. In'this case there would still-be-a necessity of maintaining proper phase relationship between the carrier energies supplied to bridge Ml so that the full carrier frequency wouldproperly be carried by central antenna 2. Accordingly, under such circumstances, the loose couplingarrangement of my invention would still app y- There also will occur to those skilled in the art many other applications of the broad principles of my invention as set forth in the objects thereof and in the appended claims.

What is claimed is:

r 1. In a radio signaling system comprising a source of. radio frequency energy, a coupling line 2 for supplying said radio frequency energy to a load, means for modulating said energy with a first signal whereby modulation of said first signal exists in said coupling line, an electronic The side band energy at voice frequency is such that it as well as the carrier frequency is balanced out modulating means for modulating said radio frequency energy with a second signal independently of said first signal, and means for supplying energy modulated with said. first signal and energy with said second signal toloads in a predetermined phase relation; a combination for maintaining said. predetermined phase relationship despite changes in the circuit characteristics of said source comprising means for loosely coupling said coupling line to said electronic modulating means to apply thereto radio frequency energy at a predetermined amplitude, means for biasing said electronic modulating means to operate substantially at saturation upon application of said radio frequency energy, whereby said modulation or-said first signal is substantially eliminated in said electronic modulating means, a second signal source for producing said second signal and means for applying, signals from said second signal source to said electronic modulating means.

2. A signaling system according to claim 1, wherein said electronic modulator comprises a vacuumtube amplifier having a grid, an anode, a grid circuit, means'for applying said radio frequency energy to said. grid circuit, an anode circuit and means for applying said second signals tosaid'anode circuit to plate modulate the energy applied to said grids.

3. In a radio signaling system, means for supplying different modulations on a carrier from a single source comprising first a source of radio frequency energy, a carrier output line coupled to said source, a four terminal bridge network having one terminal coupled to said carrier output line, a balancing network coupled to the diagonally opposite terminal of said bridge, signal output lines coupled to the other diagonally disposed termi-nals ofsaid bridge, first modulating means in each'of .said signal output lines, whereby certain percentage of modulation exists in said carrier output line, electronic modulator means, means loosely coupled to said carrier outputlin'e for supplying radio frequency energy to. said electronic modulator means, said electronicxmodulator means having such bias that'said radio frequency energy operates said modulator means at saturation, whereby modulation effects from'said first modulating means is. substantially elimi- 'nated second signal means, andmeans for applying energy from said second signal means to said electronic modulator means to modulate the radio frequency supplied thereto.

4. In a radio beacon including a source of radio frequency energy, an antenna array comprising outer antenna elements and a central antenna element, first means for supplying energy from said source to said antenna elements to provide a course indicating signal, second means for supplying energy from said radio frequency source to said central antenna unit in predetermined phase With respect to energy from said first means, means for modulating energy in said first means With course identification signals, and electronic modulator means for modulating energy in said second means to provide other typesof signals, circuit connections for maintaining said predetermined phase relation comprising a coupling line from said source to said first modulator whereby said radio frequengy energy carrying a percentage modulation of saga course identification signals are present in saifigi line, coupling means for coupling said couplin line to said electronic modulator means to caus substantial saturation of said electronic modu l l l lator means to substantially eliminate said course identification modulation, a source of said other types of signals, and means for coupling said source of signals to said electronic modulator to modulate said radio frequency energy with said other types of signals.

5. A radio beacon according to claim 4 wherein said electronic modulator comprises a vacuum tube amplifier having a grid, an anode, a grid circuit, means for applying said radio frequency energy to said grid circuit, an anode circuit and means for applying said second signals to said anode circuit to plate modulate the energy applied to said grids.

FRANK J. LUNDBERG.

REFERENCES CITED 7 The following references are of record in the '7 file of this patent:

UNITED STATES PATENTS Number Name Date 2,283,677 Kandoian May 19, 1942 2,327,435 Kandoian Aug. 24, 1943 2,283,897 Alford May 26, 1942 

